Apple is taking a stance against scammers.
Moving forward, once an app is approved, iTunes Connect will not allow designers to update the screen shots of an app unless they submit a new version for approval. Basically this means that screen shots must go through the approval process in order to appear in the app's profile within iTunes.
This decision was made to confront a common scam tactic that happens with the app market. Users often mistakenly purchase fake apps with screenshots stolen from more popular or non-iOS games--for example the various apps titled Halo 4 on the iTunes app market that turned out to be a puzzle or car game. The tricky game designers or scammers would start by submitting their actual, simple app and then change the details after the release--including screen shots of the more popular game.